The first large and comprehensive study of the genetics of a common lung cancer has found that more than half the tumors from that cancer have mutations that might be treated by new drugs that are already in the pipeline or that could be easily developed. For the tens of thousands of Americans with that cancer — squamous cell lung cancer — the results are promising because they could foretell a new type of treatment in which drugs are tailored to match the genetic abnormality in each patient, researchers say.